Multiple Complex Developmental Disorder (MCDD) is a well-defined and validated behavioral subtype of autism with a proposed elevated risk of developing a schizophrenic spectrum disorder. The current study investigated whether children with MCDD show the same deficits in sensory gating that are commonly reported in schizophrenia, or whether they are indistinguishable from children with autism in this respect. P50 suppression and prepulse inhibition (PPI) of the startle reflex were assessed in children with MCDD (n=14) or autism (n=13), and healthy controls (n=12), matched on age and IQ. All subjects showed high levels of PPI and P50 suppression. However, no group differences were found. No abnormalities in sensory filtering could be detected in children with autism or MCDD. Since sensory gating deficits are commonly regarded as possible endophenotypic markers for schizophrenia, the current results do not support a high level of similarity between schizophrenia and MCDD.